Stabilization of propylene



United States Patent 3,345,327 STABILIZATION 0F PROPYLENE Martin Dexter,Briarcliflf Manor, and Kathleen D.

Schafer, Bronx, N.Y., assignors to Geigy Chemical Corporation,Greenburgh, N.Y., a corporation of Delaware No Drawing. Originalapplication June 6, 1964, Ser. No. 373,078. Divided and this applicationMay 11, 1965, Ser. No. 462,467

3 Claims. (Cl. 260-45.85)

This application is a divisional application of our copendingapplication Ser. No. 373,078, filed June 6, 1964, now abandoned, whichis a continuation-impart of our copending application, Ser. No. 188,275,filed Apr. 17, 1962, now abandoned.

The present invention pertains to certain diesters, to compositionswhich are stabilized by these diesters and to various novel uses ofthese diesters.

In particular, this invention pertains to compounds of the formula:

in which:

R is alkyl of from 8 to 18, preferably 12 to 18 each of R and R if alkylfrom 12 to 30 carbon atoms,

preferably 12 to 18 carbon atoms, and

n has a value of zero to one.

R R and R may be the same or may be different and include, insofar asdefined above, such alkyl groups as octyl, nonyl, decyl, undecyl,dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl,tetracosyl, pentacosyl, hexacosyl, heptaeosyl, octacosyl, nonacosyl andtriaconyl. Embraced within these groups are both the straight and branchchain alkyl groups.

'The compounds of the present invention have as their characteristicproperty the ability to vastly improve the eifect of numerous othercompounds which are used as stabilizers for organic material norm-allysubject to deterioration. Thus while the compounds of the presentinvention may be considered as stabilizers in their own right, theirproperties are such that they would be more conventionally classified assynergists in that when combined with known stabilizers, they exhibitthe ability to increase to total stabilization to a degree far exceedingthat which could be expected from the additive properties of theindividual components.

Organic materials Which, being normally subject to deterioration, areoften stabilized by the addition of various stabilizing compound andwhich therefore are suitable -for the further addition of compounds ofthe present invention include for example synthetic organic polyrnericsubstances such as vinyl resins formed by the polymerization of vinylhalides or from the copolymerization of vinyl halides with unsaturatedpolymerizable compounds, e.g., vinyl esters, a ti-unsaturated esters,oz,,6- unsaturated acids, a,;8-unsaturated ketones or aldehydes andunsaturated hydrocarbons such as butadiene and styrene; poly-tx-olefinssuch as polypropylene, polyethylene, polybutylene, polyisoprene and thelike, including copolymers of a-olefins; polyurethanes such as areprepared from polyols and organic polyisocyanates; polyamides such aspoly(hexamethylene adipamide); polyesters such as poly(methyleneterephthalates); polycarbonates; polyacetals; polystyrene; poly(ethyleneoxide); copolymers such as those formed by the copolymerization ofacrylonitrile, butadiene and/or styrene; as well as Patented Oct. 3,1967 physical mixtures of the above such as high impact polystyrenecontaining copolymers of butadiene and styrene; urea-formaldehyde-alkydfinishes and the like.

Other materials so stabilized include lubricating oils such as those ofthe aliphatic ester type, e.g., dihexyl amlate,di-(Z-ethylhexyl)azelate, di-(3,5,5-trimethylhexyl) glutarate, di (3,5,5-trimethylpentyl)-glutarate, di-(Z- ethylhexyl)pimelate,di-(2-ethylhexyl)-adipate, diisoamyl adipate, triarnyl tricarballate,pentaerythritol tetracaproate, dipropylene glycol dipelargonate,1,5-pentanediol di- (Z-ethylhexanoate), and the like; fats and oils ofanimal and vegetable origin, e.g., linseed oil, menhaden oil, cod liveroil, castor oil, olive oil, rapeseed oil, coconut oil, palm oil, cornoil, sesame oil, peanut oil, cotton seed oil, butter, fat, lard, beeftallow and the like; saturated and unsaturated hydrocarbons such as forexample, both natural and synthetic gasolines, jet fuels, diesel oils,mineral oils, fuel oils, drying oils, waxes and resins.

The compounds of this invention exhibit their novel properties whencombined with a wide variety of stabilizers, some of which are known andsome of which are the subject of copending applications. Primarily theseare of the broad class of phenolic antioxidants.

Typical of the phenolic antioxidants whose stabilizing properties areimproved by the addition of the compounds of the present invention, arethe following:

CLASS A.PHENOLIC TRIAZINE STABILIZERS 6- (4-hydroxy-3-methyl-5-t-buty1anilino-2,4-bis- (n-octylthio 1,3,5 -triazine 6-(4-hydroxyanilino -2,4-bis- (n-octylthio) 1,3,5 -triazine 6-(hydroxy-3,5-dimethylanilino -2,4-bis- (n-octylthio 1,3 ,5 -triazine 6-4-hydroxy-3,5-di-t-butylanilino -2,4-bis- (n-octylthioethylthio) -1,3,S-triazine 6- (4-hydroxyphenoxy -2,4-bis- (n-octylthio) 1,3 ,5 -triazine2,4-bis- (4-hydroxy-3,S-di-t-butylphenoxy fi-(n-octylthio)-1,3,5-triazine 2,4,6-tris- (4-hydroxy-3,S-di-t-butylphenoxy)1,3,5-triazine 6- (4-hydroxy-3 ,5 -di-t-butylanilino) -2,4 bis-(phenoxy) -1,3,5-triazine 6- (4-hydroxy-3,S-di-t-butylanilino t-4-(4-hydroxy-3,5-dit-butylphenoxy) -2- (n-octylthio) -1,3,5-triazine' 2,4, 6-tris- 4-hydroxy-3,S-di-t-butylphenoxy) 1, 3 5 -triazine 6-(4-hydroxy3,S-di-t-butylphenoxy) -2,4-bis- (n-octylthioethylthio) -1,3,5 -triazine 6- (4-hydroxy-3 ,5'-di-t-butylanilino -2,4-bis-(n-octylthio) -1,3 ,5 -triazine 6- (4-hydroxy-3-methylphenoxy -2,4-bis-(n-octylthio 1,3 ,5 -triazine 6- (4-hydroXy-3 -t-butylphenoxy -2,4-bis-(n-octylthioethylthio)-1,3,5-triazine 6- (4-hydroxy-3-methyl-5-t-butylphenoxy -2,4-bis (noctylthio l ,3,5-triazine 2,4-bis-(4-hydroxy-3 -methy1-5-t-butylphenoxy) -6-(noctylthio) -1,3,5-triazine2,4,6-tris-(4-hydroxy-3-methyl-S-t-butylphenoxy) -1,3,5-

triazine 2,4-bis- (4-hydroxy-3,5-di-t-butylphenoxy -6-amino 1,3,5 -triazine 2,4-bis- (4-hydroxy-3,S-di-t-butylphenoxy) -6-dimethylamino- 1,3,5 -triazine 2,4-bis- (4-hydroxy-3 ,5 -di-t-butylphenoxy)-6-dodecylamino-1,3,5-triazine2,4-bis-'(4-hydroxy-3,S-di-t-butylphenoxy) -6-(di-2-ethylhexyl)amino-1,3 ,5 -triazine 2,4-bis- 4-hydroxy-3 ,5 -di-t-butylphenoxy)-6-dibutylamino-1,3,5-triazine 2,4-bis (4-hydroxy-3,S-di-t-butylanilino)-6-(n-octy1thio) 1,3,5-triazine 6- (4-hydroXy-3 ,S-di-t-butylphenoxy)-2,4-his- (n-octylthiopropylthio l ,3,5-triazine 6- (4-hydroxy-3,5-di-t-butylphenoxy) -2,4-bis- (n-dodecylthioethy1thio)-1, 3 ,5 -triazine2,4-bis- (4-hydroXy-3,S-di-t-butylphenoxy -6-butylthio- 1,3 ,5 -triazine2,4-bis- (4-hydroxy-3,5-di-t-butylphenoxy) -6- (n-octadecylthio-l,3,5-triazine 2,4-bis- (4- hydroXy-3 ,S-di-t-butylphenoxy)-6-(n-dodecy1- thio 1,3,5 -triazine 2,4-bis- (4-hydroxy-3 ,5-di-t-butylphenoXy) -6- (n-octylthiopropylthio -1, 3 5 -triazine2,4-bis- (4-hydroxy-3 ,5 -di-t-butylphenoxy) -6- (n-octylthioethylthiol, 3 ,5 -tri azine 2,4-bis-( 4-hydroXy-3 ,5 -di-t-butylphenoxy -6-(n-dodecylthioethylthio -1, 3 ,5 -triazine The above phenolic triazinestabilizers are more fully described in the copending application ofMartin Dexter et al., Ser. No. 361,533, filed Apr. 21, 1964, now US.3,255,191.

CLASS B.PHE-NOLIC PHOSPHONATE STABILIZERS Among the many phosphonatestabilizers whose properties are improved by the addition of compound ofthe present invention are the di-(lower)alkyl phosphonates disclosed inUS. Patent No. 3,006,945. Particularly valuable phenolic phosphonates inthis regard however are the di-(higher)alkyl phenolic phosphonatcs,i.e., having from 14 to 30 carbon atoms in each alkyl group.Representative of these are the following:

Di-n-octadecyl 3-t-butyl-4-hydroxy-S-methylbenzylphosphonateDi-n-octadecyl 1-(3,5-di-t-butyl-4-hydroxyphenyl)-ethane phosphonateDi-n-tetradecyl 3,5-di-t-butyl-4-hydroxybenzylphosphonate Di-n-hexadecyl3,5-di-t-butyl-4-hydroxybenzylphosphonate Didoc'osyl-3,5-di-t-butyl-4hydroxybenzylphosphonate Di-n-octadecyl3,5-di-t-butyl-4-hydroxybenzylphosphonate The above di-(higher)alkylphenolic phosphonates are more fully described in the copendingapplication of John Spivack, Ser. No. 308,345, filed Sept. 12, 1963, nowabandoned.

CLASS C.--PHENOLIC ESTER STABILIZERS Sub-class C-I n-Octadecyl3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate n-Octadecyl3,5-di-t-butyl-4-hydroxyphenylacetate n-Octadecyl3,5-di-t-butyl-4-hydroxybenzoate n-Hexyl3,5-di-t-butyl-4-hydroxyphenylbenzoate n-Dodecyl3,5-di-t-butyl-4-hydroxypheny1benzoate Neo-dodecyl 3-(3,5-di-tbutyl-4-hydroxyphenyl)-propionate Dodecyl ,8- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate Ethyl11-(4-hydroXy-3,5-di-t-butylphenyl)-isobutyrate Octadecyla-(4-hydroXy-3,S-di-t-butylphcnyl)-isobutyrate Octadecyla-(4-hydroxy-3,S-di-t-butylphenyl)-propionate Sub-class C-ll2-(n-octylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate2-(n-octylthio)ethy1 3,5-di-t-butyl-4-hydroxyphenylacetate2-(n-octadecylthio)ethyl 3,5 -di-t-butyl-4-hydroxyphenylacetate 2-(n-octadecylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate2-(2-hydroxyethylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoatefl,fi-Thiodiethyl bis(3,5-di-t-butyl-4-hydroxyphenylacetate) Diethyleneglycol bis-[3-(3,5-di-t-butyl-4- hydroxyphenyl) propionate] 2-(n-octadecylthio) ethyl 3- 3,5 -di-t-butyl-4- hydroxyphenyl) propionateThio-bis- [ethylene 3 3,5 -di-t-butyl-4-hydroxyphenyl)propionate]Stearamido N,N-bis- [ethylene 3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate] n-Butylimino N,N-bis-[ethylene 3-(3,5-di-t-butyl-4-hydroxyphenyl propionate] 2-(2-stearoyloxyethylthio)ethyl 3,5-di-t-butyl- 4-hydroxybenzoate 2-(2-hydroxyethylthio) ethyl7-(3-methyl-5-tbutyl-4-hydroxyphenyl)heptanoate 2-2-stearoyloxyethylthio ethyl 7- 3-methyl- 5 -t-butyl-4-hydroxyphenyl)heptanoate Subclass C-III 1,2-propylene glycol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl pro p ionate] Ethylene glycol bis-[3-( 3,5-di-t-buty1-4-hydroxyphenyl propionate] Neopentylglycol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl propion ate] Ethylene glycol bis-(3,S-di-t-butyl-4-hydroxyphenylacetate) Glycerine-1-n-0ctadecanoate-2,3-bis-'(3,5-

di-t-butyl-4-hydroxyphenylacetate) Tetra- [methylene 3- 3 ,5-di-t-butyl-4- hydroxyphenyl propionate] methane n-Propyl1,1,1-tris-[methylene 3-(3,5-dit-butyl-4-hydroxyphenyl)propionate]Sorbitol heXa-'[3-(3,5-di-t-butyl-4-hydroxyphenyl propionate]1,2,3-butanetriol tris- [3-( 3,5 -di-t-butyl- 4-hydroxyphenylpropionate] 2-hydroxyethyl 7-(3-methyl-5-t-butyl-4-hydroxyphenyl)heptanoate 2-stearoyloxyethyl 7-(3-methyl-5-t-butyl-4-hydroxyphenyl heptanoate The above phenolic ester stabilizers ofsub-classes C-I, C-II and CIII are more fully described in the copendingapplications of Martin Dexter et al., Ser. No. 354,434, filed Mar. 24,1964, Ser. No. 354,464, filed Mar. 24, 1964 and Ser. No. 359,460, filedApr. 13, 1964, respectively.

CLASS D.-PHENOLIC HYDROCARBON STABILIZERS 4,4-butylidene-bis-6-t-butyl-m-cresol) 4,4-thio-bis- 6-t-butyl-m-cresol)4,4'-methylene-bis- 2,6-di-t-butylphenol) 2, 2'-methylene-bis[4-hydroXy-6-( l-methylcyclohexyl )phenol] 1,3 ,5 -trimethyl-2,4,6-tris-(4-hydroXy-3,5 -di-tbutylb enzyl) benzene 2, 6-di-t-butyl phenol 1, 1,3-tris- (5 -t-butyl-4-hydroxy-2-methylphenyl) butane4,4-isopropylidene-bis- (Z-t-butylphenol) The above phenolic hydrocarbonstabilizers are known and many are commercially available.

In addition to one or more of the above phenolic sttabilizers, it isoften advantageous to employ other additives such as ultraviolet lightabsorbers, e.g., 2-hydroXy-4- methoxybenzophenone,2-(2-hydroxy-5'-rnethylphenyl) benztriazole, etc.; various phosphitecompounds such as trioctylphosphite, dilaurylphosphite,tris(nonylphenyl) phosphite and the like. Such two, three or fourcomponent systems, when including a compound of the present in'-'vention, exhibit far superior properties to the additive properties ofthe individual components.

Other materials often added to such organic materials, depending uponthe substrate, include pourpoint depressants, corrosion and rustinhibitors, metal deactivators, demulsifiers, antifoam agents, carbonblack, accelerators,

plasticizers, color stabilizers, heat stabilizers, dyes, pigments andthe like.

The dialkyl alkylthiodiesters of the present invention are preferablyused in a concentration of from 0.005% to about 10% by weight of thetotal composition together with one or more of the above phenolicantioxidants, one or more ultraviolet light absorbers and/or one or moreof the above phosphite compounds. These are particularly useful insynthetic organic polymeric substances such as polypropylene,polyethylene, polystyrene and the like to protect such substances fromdeterioration both during use and during processing such as millingpolypropylene or blow molding polyethylene. The compounds of the presentinvention exhibit superior compatability in diverse substrates withlittle or no odor formation.

The compounds of the Formula I may be prepared from maleic anhydride oritaconic anhydride and a suitable alcohol in the presence of p-toluenesulfonic acid to yield the corresponding diester. 'Ihe diester of maleicacid or itaconic acid so obtained is then reacted with an alkylmerc-aptan in the presence of sodium methylate'to yield the diester ofan alkylrnercaptosuccinic acid or of an alkylmercaptomethylsuccinicacid. Alternatively mercaptosuccinic acid of mercaptomethylsuccinic acidmay be reacted with an alcohol or the mixture of alcohols. In anotherprocess, the alkylmercaptosuccinic acid or alkylmercaptomethylsuccinicacid is reacted with a suitable alcohol to yield the desired diester.Suitable methods of making certain of the compounds of the Formula I arealso illustrated by US. Patents 2,561,673 and 2,581,514.

The following examples, presented for illustration and not limitation,will further serve to typify the nature of the present invention. Inthese examples, parts are by weight unless otherwise indicated and therelation of parts by weight to parts by volume as is that of grams tocubic centimeters. Temperature is expressed in degrees centigrade.

Example 1.Diddecyl n d0decylthi0succindte (a) Maleic anhydride (24.5part-s), dodecyl alcohol (102.6 parts) and p-toluene sulfonic acid (1.1parts) are refluxed in 100 parts by volume of benzene and the waterformed is removed as azeotrope. In this manner 4.4 parts by volume ofwater are obtained (theory 4.5 parts) and the acid number is constantafter 1% hours. The benzene is then removed in vacuo, whereupon theresidue crystallizes. The didodecyl maleate thus obtained isrecrystallized from ethanol to give 95.7 parts of didodecyl maleate,M.P. 2830 C.

(b) To 0.14 part of sodium methylate in 5 parts by volume of methanolare added 10.1 parts n-dodecylmercaptan. Didodecyl maleate (22.6 parts)is then added with stirring and cooling so that the temperature does notexceed 34. The reaction mixture is set aside for several days and thenslurried with 20 parts by volume of water and filtered. This material isthen evaporated to dryness and recrystallized from isopropanol to yielddidodecyl n-dodecylthiosuccinate, M.P. 3638 C.

Calculated: C, 73.33; H, 12.01; S, 4.89. Found: C, 73.30; H, 12.37; S,4.98.

Example 2.--Di(n-octadecyl) n-dodecylthiosuccinate (a) To a mixture of86.1 parts of diethyl maleate and 101.2 parts of n-dodecylmercaptan areadded 4 drops of a 40% solution of benzyltrimethylammon-ium methoxide inmethanol. The temperature rises to approximately 75 and the reactionmixture is then allowed to cool to room temperature and is filtered.

The product, diethyl n-dodecylthiosuccinate, distills at 140-146 C./0.05 mm.

Calculated: C, 64.07; H, 10.31. Found: C, 64.13; H, 10.22.

(b) Diethyl n-dodecylthiosuccinate (11.24 parts) and 16.23 partsn-octadecyl alcohol are refluxed in 50 parts by volume of toluene toremove any water present. So-

dium methylate (0.5 part) is then added and the reaction mixture heatedto transesterify and remove the ethanol formed as an ethanol-tolueneazeotrope. After the theoretical amount of ethanol has been obtained,the reaction mixture is diluted with 50 parts by volume of toluene,filtered hot and concentrated. The di(n-octadecyl)n-dodecylthiosuccinate thus obtained solidifies on standing and isrecrystallized from isopropanol, M.P. 42-44 C.

By utilizing an equivalent amount of n-octylmercaptan forn-dodecylmercaptan in part (a) of this example and thereafter executingthe procedure of part (b), there is obtained di(n-octadecyl)n-octylthiosuccinate.

Example 3.-Di(n-d0decyl) n-oetadecylthiosuccinate Diethylmaleate (12.91parts) and 12.5 parts of octadecylmercaptan are allowed to react in thepresence of benzyltrimethylammonium methoxide according to the procedureof Example 2(a). The diethyl n-octadecylthiosuccinate thus obtained isthen treated with n-dodecyl alcohol (11.18 parts of alcohol to 13.76parts of diester) according to the procedure of Example 2(b) to yielddi(n-dodecyl) n-octadecylthiosuccinate, M.P. 4l42 C.

Example 4.Didodecyl dodecylthiomethylsuccinate (a) Twenty-eight parts ofitaconic anhydride, 93.2 parts of n-dodecyl alcohol, 1 part of p-toluenesulfonic acid, 0.56 part of hydroquinone and parts by volume of tolueneare refluxed for 3 /2 hours, collecting the toluene-water azeotropewhich is formed. The reaction mixture is then clarified with charcoaland the toluene next removed under reduced pressure, employed a bathtemperature of about 60 C. The residue is allowed to solidify and isthen recrystallized from hexane to yield didodecyl itaconate.

(b) To a reaction vessel equipped with a mechanical stirrer are added43.98 parts of n-dodecylmercaptan. This is warmed to about 40 C. and0.71 part of sodium methoxide are added. Didodecyl itaconate, obtainedin part (a) of this example, is melted and added dropwise to thereaction mixture over a. period of approixately 1 hour so as to maintaina reaction temperature of from 40-45 C. At the end of this time thereaction mixture is dissolved in parts by volume of toluene and a smallamount of glacial acetic acid is added to discharge the green color. Thetoluene solution is then extracted with 50 parts by volume of a 10%aqueous solution of sodium bicarbonate and washed with water until aneutral wash is obtained. The organic layer is separated, clarified,dried over magnesium sulfate and filtered. The toluene is removed fromthe filtrate under reduced pressure and the residue recrystallized froma mixture of about 600 parts by volume of isopropanol and about 50 partsby volume of methanol and dried to yield didodecyldodecylthiomethylsuccinate, M.P. 34-35 C.

In a similar fashion from equivalent amount of the appropriate alkanoland alkyl mercaptan, there are respectively obtained the compoundsdidodecyl octylthiomethylsuccinate, didodecyloctadecylthiomethylsuccinate, dioctadecyl dodecylthiomethylsuccinate,M.P. 5l.5-53 C., and dioctadecyl octadecylthiomethylsuccinate, M.P.60.5-63" C.

Example 5.-Did0de'cyl octadecylthiomethylsuccinate By employingequivalent amount of diethyl itaconate for diethyl maleate in theprocedure of Example 3, there is obtained didodecyloctadecylthiomethylsuccinate, M.P. ca. 30 C.

Example 6.Stabilization of polypropylene 'Unstabilized polypropylenepowder (Hercules Profax 6501) is thoroughly blended 'with 0.5% by weightof didodecyl n-dodecylthiosuccinate and 0.1% by weight of 6 (4hydroxy-3,S-di-t-butylanilino) 2,4-bis-(n-octylthio)-1,3,5-triazine. Theblended material thereafter is milled on a two roller mill at 1 82 C.for 6 minutes,

after which time the stabilized polypropylene is sheeted from the milland allowed to cool.

The milled polypropylene sheet is cut into small pieces and pressed for7 minutes on a hydraulic press at 218 C. and 174 lbs./in. The resultantsheets of 25 mil thickness are then tested for resistance to acceleratedaging in a forced draft oven at 149 C. The stabilized polypropyleneisnot subject to deterioration after 600 hours in the oven while theunstabilized material deteriorates after about 3 hours; polypropylenestabilized with 0.5% didodecyl ndodecylthiosuccinate alone, failed after23 hours; with 0.1% of 6 (4-hydroxy-3,S-di-tbutylanilino)-2,4-bis-(noctylthio)-1,3,5-triazine alone after 56 hours.

The so stabilized polypropylene is not subject to embrittlement orcrazing upon exposure in the Fade-OaMeter after more than 150 hours, anddoes not discolor appreciably during this time.

At elevated temperatures, for example about 300, the so stabilizedpolypropylene exhibits very good processing stability and very littlepolymer degradation as compared to the unstabilized polypropylene.

In the same manner, polypropylene is stabilized with 0.5 of didodecyldodecylthiosuccinate and 0.1% of din octadecyl3,5-di-t-butyl-4-hydroxybenzylphosphonate (weight percent).

The polypropylene composition is stabilized against deterioration forover 2000 hours. The unstabilized polypropylene deteriorates after 3hours, while when 0.1% by weight alone ofdi-n-octadecyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate is used, thecomposition is stabilized for 20 to 30 hours.

Didodecyl dodecylthiomethylsuccinate at a concentration of .5%- byweight and 2,4-bis-(3,5-di-tbutyl-4-hydroxyphenoxy)-6-noctylthio-1,3,5-triazine at a concentrationof 0.1% weight when combined in polypropylene in the same fashionstabilize the composition in excess of 2000 hours Whereas the individualcomponents stabilize comparable compositions for about 105 and 280 hoursrespectively. Comparable compositions of didodecyloctadecylthiomethylsuccinate are stabilized for over 16-00 hours whereasthis compound alone stabilizes for only 95 hours. Dioctadecyldodecylthiomethylsuccinate and dioctadccyl octadecylthiomethylsuccinateboth each stabilize when in combination with this phenolic antioxidantin excess of 1600 hours while alone each stabilizes for only 110 hours.

Similarly when .5 by weight of didodecyl dodecylthiomethylsuccinate and0.1% of dioctadecyl 3,5-di-tbutyl-4-hydroxybenzylphosphonate areincorporated in polypropylene, the composition is stabilized for over1500 hours whereas the former component when utilized alone stabilizesonly for 20 to 30 hours. A comparable composition alternativelyemploying didodecyl octadecylthio methylsuccinate and this phenolicphosphonate is stabilized for over 900 hours whereas compositionsutilizing only the former is stabilized for hours.

The above percentages are not critical but are merely given by way ofconvenience.

What is claimed is:

1. A composition consisting essentially of polypropylene, a stabilizingamount of a phenolic antioxidant, and from about .005 to about 10% of acompound of the formula R and R are each alkyl of from 12 to 20 carbonatoms; and

n is zero or 1.

2. A composition as claimed in claim 1 wherein the compound of Formula Iis didodecyl'dodecylthiosuccinate. 1 3. A composition as claimed inclaim 1 wherein the compound of Formula I is didodecyldodecylthiomethylsuccinate.

References Cited UNITED STATES PATENTS 7 Kluge 25248.6

LEON D. ROSDOL, Primary Examiner.

M. WEINBLATT, Assistant Examiner.

1. A COMPOSITION CONSISTING ESSENTIALLY OF POLYPROPYLENE, A STABILIZINGAMOUNT OF A PHENOLIC ANTIOXIDANT, AND FROM ABOUT .005 TO ABOUT 10% OF ACOMPOUND OF THE FORMULA